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X-ray CCD Cameras for Soft X-ray Imaging
Application # 1: Soft X-Ray Microscopy
The short wavelength of soft X-rays offers the possibility of microscopes which provide resolution near that of an electron microscope, but without the complex sample preparation requirements. The detailed structure of soft X-ray absorption spectra also suggests that microscopes will be able to achieve element-specific imaging, thus providing insight into the composition of the structures imaged. Typical energy range (water window) 280540 eV (23-45 Angstroms). Percent of photons detected 100 80 Silicon L-edge 100.6 eV 1,240

SX-TE/CCD-512SB SX-TE/CCD-1024SB

Photon Wavelength (е) 12.4 124

1.24

60

Silicon K-edge 1.8 keV 40 20

Special Applications

Application # 2: Soft X-Ray Photolithography of Semiconductors
The short wavelength of soft X-rays can potentially decrease the feature sizes of circuits produced in semiconductors relative to optical methods in use now. Soft Xray sensitive cameras can be used to image photomasks, characterize photoresists and sources, and monitor soft X-ray spectra.

0 10 100 1,000 Photon energy, eV 10,000

Soft X-ray quantum efficiency, Model SX-TE/CCD Estimated from data and theory 1,240 Photon Wavelength (е) 124 12.4 1.24

Electrons in CCD/X-ray photon detected

10,000

1,000

Application # 3: Plasma Physics
Plasmas in tokamaks and other experiments frequently emit substantial soft Xray flux. This can be used to image or spectroscopically characterize the plasma, including impurities which may contribute to energy transport.

100

10

Detection Requirements for These Applications
Sources are typically pulsed, such as short lived laser produced plasmas, with limited soft X-ray yield. High quantum efficiency and high resolution are important performance parameters.

1 10 1,000 X-ray energy, eV Soft X-ray detection gain, best estimate is 1e-/3.65 eV 100 10,000

Camera Configuration
These cameras are provided with an open ended nose, with a flange for direct connection of the camera to your vacuum system. The CCD is oriented for detection at near normal incidence.

X-Ray Detection Mechanism for These Cameras
Direct detection of X-ray photons in the silicon of a special back illuminated CCD. This approach offers higher resolution and higher QE than open microchannel plate detectors. 78

used during CCD operation with soft Xrays. The CCD camera controller can continuously clean the CCD until a trigger is received. This prevents buildup of dark current and unwanted signal prior to the Xray pulse. Readout can follow immediately after the trigger. For testing and familiarization with the operation of these cameras, they are also provided with a conventional sealed vacuum nose, for optical operation (i.e. with a lens). For this type of operation, a standard camTel: 609-587-9797

Shuttering and Synchronization
Because there is a continuous high vacuum between the source and CCD, no shutter is Princeton Instruments


era mounted optical shutter is also provided.

Cooling
These cameras use multistage peltier devices to cool the CCD array. Heat output from the Peltier stack can be removed by water circulation or (optionally) forced air.

valve between the camera and the rest of the system. Also, cryogenic traps are highly recommended, to prevent contamination.

a factor of 2-4в for photon counting performance. Note #2: Low energy X-ray photons are highly absorbed in silicon. This results in signal generation in backilluminated CCD arrays which is very close to the back surface. The closer that charge is generated to the back surface, the more problematic charge transfer to the front surface becomes. At energies above the Silicon kalpha and L-alpha edges (1.8 keV and 100.6 eV respectively) absorption is particularly strong. This may result in an apparent QE decrease and response nonuniformity increase at these energies. Note #3: Princeton Instruments has been shipping special back illuminated CCD cameras for soft X-ray detection since 1990. We continue to work with new state of the art CCD arrays. Contact one of our application physicists for the most up to date results.

Special Configurations
By special order, CCD arrays can be mounted for grazing angle detection. Quantum efficiency and other performance parameters may change in this configuration. Cameras with cryogenic (liquid nitrogen) cooling can also be provided. These are recommended when weak signals from many laser shots must be integrated onchip, or when spectroscopic binning will be used, such as for operation with a crystal spectrograph.

Damage and Protection
Exposure of the CCD surface to X-rays can eventualy damage the CCD. Exposure to photons with more than 1.8 keV energy (silicon k-alpha) will accelerate damage significantly. Princeton Instruments cameras for soft X-ray work incorporate shields to prevent exposure of the most damage sensitive portions of the CCD array to Xrays, while maintaining as much open imaging area as possible. Because the cooled surface of the CCD can become contaminated by vacuum venting, customers are advised to position a gate

Additional Performance Notes
Note #1: Some X-ray photons will result in signal which is divided over more than one pixel, so the criteria below do not guarantee detection of all photons over the energies listed above the read noise. Allow

Performance Specifications
CCD Arrays: Model SX-TE/CCD-512SB, SITe 502A back illuminated, special surface treatment, MPP only; SX-TE/CCD-1024SB, SITe ST-003 back illuminated, special surface treatment, MPP only Electrical, 512 в 512 pixels for 512SB, 1024 в 1024 pixels for 1024SB; X-Ray with shield, 512 x 450 pixels (12.3 в 10.8 mm) for 512SB, 1024 в 960 pixels (24.6 x 23.1 mm) for 1024SB 24 в 24 µm Electrical, 350,000 electrons; X-ray, 3,500 photons at 365 eV 50 kHz, electrical, 4-8 electrons RMS, X-ray, < 1 photon signal peak-to-peak for energies over 150 eV (See note #1 above) 1 MHz, electrical, 20 electrons RMS, X-Ray, < 1 photon signal peak-to-peak for energies over 365 eV (See note #1 above) SITe Grade 1 arrays are used. These arrays are, however, graded by SITe using visible light illumination (not with X-rays). Response nonuniformity and defects, when used to detect soft X-rays, may not be the same. 1 electron/pixel-second at -50°C (water cooled) 4 electron/pixel-second at -40°C (air cooled)

Special Applications

Format:

Pixel Size: Full Well Capacity: Readout Noise:

Blemish Specification & Response Uniformity: Dark Current (average excluding defects):

Fax: 609-587-1970

Princeton Instruments

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